Amoxicillin Dosing for Pediatric Patients
The correct dosage calculation for amoxicillin in children is weight-based, with 45-90 mg/kg/day divided into 2-3 doses depending on the infection severity, with higher doses for respiratory infections and areas with high pneumococcal resistance. 1
General Dosing Principles
- Amoxicillin dosing should always be calculated based on the child's body weight rather than age for accurate dosing 2
- Dosing should be started at the beginning of a meal to minimize gastrointestinal intolerance 3
- Treatment should generally continue for a minimum of 48-72 hours beyond symptom resolution 3
- For Streptococcus pyogenes infections, treatment should continue for at least 10 days to prevent acute rheumatic fever 3
Dosage Calculation by Age Group and Weight
Children ≥3 months and <40 kg:
Mild/Moderate Ear, Nose, Throat, Skin, or Genitourinary Infections:
- 25 mg/kg/day divided every 12 hours OR
- 20 mg/kg/day divided every 8 hours 3
Severe Infections or Lower Respiratory Tract Infections:
- 45 mg/kg/day divided every 12 hours OR
- 40 mg/kg/day divided every 8 hours 3
Respiratory Infections with Risk of Resistant Pneumococci:
Group A Streptococcal Infections:
Children <12 weeks (3 months):
- Maximum recommended dose: 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 3
Children with Renal Impairment:
- For GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours, depending on infection severity
- For GFR <10 mL/min: 500 mg or 250 mg every 24 hours, depending on infection severity 3
Practical Dosing Examples
For a 20 kg child with:
- Mild otitis media: 25 mg/kg/day = 500 mg/day ÷ 2 doses = 250 mg twice daily
- Pneumonia: 45 mg/kg/day = 900 mg/day ÷ 2 doses = 450 mg twice daily
- Severe pneumonia in area with high pneumococcal resistance: 90 mg/kg/day = 1800 mg/day ÷ 2 doses = 900 mg twice daily
Dosing Frequency Considerations
- Twice-daily dosing (b.i.d.) is a feasible alternative to three-times-daily (t.i.d.) dosing for improved compliance 5
- For twice-daily dosing, consider using 30-40 mg/kg/dose to maintain adequate time above MIC 5
- Higher doses (75-90 mg/kg/day) may be needed for acute otitis media, particularly during viral coinfection 6
Common Pitfalls in Pediatric Amoxicillin Dosing
- Underdosing: Standard doses (40-45 mg/kg/day) may be inadequate for resistant organisms, particularly in respiratory infections 6, 7
- Age-based dosing: Using age rather than weight can lead to significant dosing errors 2, 8
- Inadequate duration: Failure to continue treatment for sufficient time after symptom resolution 3
- Improper prescription information: Prescriptions should include daily dose, number of divided doses, duration of therapy, indication, and child's weight 2
By following these weight-based dosing guidelines and considering the specific infection type and local resistance patterns, clinicians can optimize amoxicillin therapy for pediatric patients.